# a = int(input())
# sum = 0
# numlist = []
# list = []
# inlist = input().split(" ")
# for i in inlist:
#     list.append(int(i))
# n = list[1]
# numlist.append(n)
# for i in list:
#     while i in numlist:
#         i = i-1
#     numlist.append(i)
# for i in numlist:
#     sum = sum + i
# print(sum)

# num = input()
# a = int(input())
# list = []
# for i in range(a):
#     list.append(int(input()))
#
# suc = 0
# succ = []
# for i in list:
#    n = 0
#    while n<len(num):
#        m = 1
#        while m<len(num):
#            if m == len(num)-1:
#                if int(num[n:]) % 1000000007 == i:
#                    suc += 1
#            elif int(num[n:m+1]) % 1000000007 == i:
#                suc+=1
#                m += 1
#            else:
#                m += 1
#        n+=1
#    succ.append(suc)
#
# for i in succ:
#     print(i)







































num = int(input())
str = input()
prenum = 0
strr = ''
strr1=''
list_str = []
list = {1:'a',2:'b',3:'c',4:'d',5:'e',6:'f',7:'g',8:'h',9:'i',10:'j',11:'k',12:'l',13:'m',14:'n',
        15:'o',16:'p',17:'q',18:'r',19:'s',20:'t',21:'u',22:'v',23:'w',24:'x',25:'y',26:'z'}
for i in range(num):
    if int(str[i]) in list:
        strr += list.get(int(str[i]))#第一种情况,全部单个数
list_str.append(strr)
while prenum <= num-1:
    if int(str[prenum]+str[prenum+1])<=26:
        strr1 += list.get(int(str[prenum]+str[prenum+1]))
        prenum+=2
    else:
        strr1 = list.get(int(str[prenum]))
        prenum += 1
list_str.append(strr1)
print



# list = input().split(" ")
# per = int(list[0])#总人数
# dis = list[1]#安全距离
# inper = 0#已感染人数
# inper_list = []
# list_x = input().split(" ")#x坐标
# list_y = input().split(" ")#y坐标
# for i in range(per):
#     if ((int(list_x[i+1])-int(list_x[i]))^2+(int(list_y[i+1])-int(list_y[i]))^2)^0.5>=dis:
#         inper += 1
# inper_list.append(inper)
#
